The present invention relates to polyarylene oligomers and polymers that display reduced thermal expansion at high temperatures. The present invention also relates to integrated circuit articles made using polyarylene dielectrics with reduced thermal expansion at high temperatures.
The semiconductor industry""s drive to continually improve performance and density has forced the use of advanced materials and interconnect structures. Interconnect performance requires the reduction of resistance and capacitance. Copper metallization was introduced in 1998 to reduce the resistance of interconnect wiring. Capacitance reduction or the introduction of low dielectric constant insulators, herein referred to as low k dielectrics, are needed for future performance enhancements.
For over 25 years, silicon dioxide has been the dielectric insulator of choice for the semiconductor industry. Silicon dioxide possesses excellent dielectric breakdown strength, a high modulus, good thermal conductivity, a low coefficient of thermal expansion, and excellent adhesion to metallic liners, plasma enhanced chemical vapor deposited (PECVD) barrier cap layers, and other like materials. However, with reduced ground rule dimensions and the need for improved performance, silicon dioxide is slowly being phased out and replaced with materials possessing lower permitivity to achieve reduced capacitance. For example, at the 180 nm technology node, fluorosilicate glass is replacing silicon dioxide in many applications.
At the 130 nm technology generation, xe2x80x9ctruexe2x80x9d low k dielectrics are being implemented into semiconductor products. There are several candidate materials but the industry has focused on two primarily: spin-on organic polymers and carbon-doped PECVD silicon dioxide dielectrics.
Polymer dielectrics may be used as insulating layers between various circuits as well as layers within circuits in microelectronic devices, such as integrated circuits, multichip modules, and laminated circuit boards. The microelectronics fabrication industry is moving toward smaller geometries in its devices to enable lower power and faster speeds. As the conductor lines become finer and more closely packed, the requirements of the dielectrics between such conductors become more stringent.
While polymer dielectrics often provide lower dielectric constants than inorganic dielectrics, such as silicon dioxide, polymer dielectrics often present challenges to process integration during fabrication. For example, to replace silicon dioxide as a dielectric in integrated circuits, the polymer dielectric must be able to withstand processing temperatures during metallization and annealing steps of the process.
Preferably, the dielectric material should have a glass transition temperature greater than the processing temperature. The dielectric must also retain the desirable properties under device use conditions. For example, the dielectric should not absorb water which may cause an increase in the dielectric constant and potential corrosion of metal conductors.
WO 98/11149 discloses dielectric polymers, which are the reaction product of a cyclopentadienone functional compound and an acetylene functional compound and are useful for microelectronics fabrication.
One shortfall of polymer dielectrics, such as the polyarylene material described in WO 98/11149, is its significant increase in the coefficient of thermal expansion, herein referred to as CTE, with increasing temperature. This significant increase in the CTE of polymer dielectrics with temperature results in a large mismatch in the CTE of the dielectric and the metal interconnect lines. Interconnect fabrication processes require multiple temperature excursions from 20xc2x0 C. to 400xc2x0 C. (and in cases 450xc2x0 C.). In the fabrication of a multilevel interconnect structures, it is common for the structure or article to be exposed to 400-450xc2x0 C. for approximately 5-10 hours. The CTE mismatch between the polymer dielectric and metal lines (copper or aluminum) stresses barrier metal liner layers, potentially resulting in liner discontinuity (i.e., breaks in the liner layer). During reliability testing, the CTE mismatch manifests during thermal cycle testing where isolated via structures fail standard reliability qualifications.
In view of the state of the art, there is a need for a modified polymer dielectric that reduces the mismatch between the CTE of the polymeric dielectric and a metal such as copper or aluminum over the entire processing range.
The present invention relates to an integrated circuit article comprising a polymer dielectric that has a minimum mismatch between the coefficient of thermal expansion of the metal (e.g., copper or aluminum) and the polymer dielectric to prevent damage in the metal via structures during thermal cycling. Thus, according to a first embodiment, the present invention relates to an integrated circuit article comprising an active substrate including, at least transistors and a pattern of metal lines forming an electrical interconnect structure wherein the metal lines are at least partially separated by a polyarylene material. In the inventive integrated circuit article, the polyarylene material is a low-k dielectric that possesses a CTE of less than 110 ppm/xc2x0 C. over the temperature range from 350xc2x0 C. to 425xc2x0 C., preferably less than 100 ppm/xc2x0 C. The term xe2x80x9clow-kxe2x80x99 is used in the present invention to denote a dielectric material having a dielectric constant of less than 3.0, preferably less than 2.6.
The inventive integrated circuit article described in the first embodiment may include a polyarylene material which is the product of Diels Alder and phenyl acetylene cure reactions between at least one compound having two or more diene functional groups and at least one compound having two or more dienophile functional groups, wherein at least one of the compounds has three or more of said functional groups.
The integrated circuit article described in the first embodiment may include a polyarylene material which is the reaction product of at least one compound having two or more cyclopentadienone functional groups and at least one compound having two or more acetylene functional groups, wherein at least one of the compounds has three or more of said functional groups.
Preferably, the integrated article described in the first embodiment includes a polyarylene material which is the reaction product of 3,3xe2x80x2-(oxydi-1,4-phenylene)bis(2,4,5-triphenylcyclopentadienone) and 1,3,5-tris(phenylethynyl)benzene.
More preferably, the integrated article described in the first embodiment includes a polyarylene material which is the reaction product of 3,3xe2x80x2-(oxydi-1,4-phenylene)bis(2,4,5-triphenylcyclopentadienone) and 1,3,5-tris(phenylethynyl)benzene wherein the stoichiometric molar ratio of the two monomers is between 0.7/1 and 0.99/1, respectively.
The second embodiment of the present invention is a cured polyarylene material which is the product of Diels Alder and phenyl acetylene cure reactions between at least one compound having two or more diene functional groups and at least one compound having two or more dienophile functional groups, wherein at least one of the compounds has three or more of said functional groups; said polyarylene material having a coefficient of thermal expansion as determined by thermal mechanical analysis of less than 110 ppm/xc2x0 C. over a temperature range of 350xc2x0-425xc2x0 C.
Preferably, the polyarylene material described in the second embodiment is one wherein the diene functional groups are cyclopentadienone groups and the dienophile functional groups are acetylene groups.
The polyarylene material described in the second embodiment may include at least one compound having dienophile functional groups which comprises a first compound that has two dienophile groups and a second compound having more than two dieneophile groups.
The polyarylene material described in the second embodiment may be a material wherein the second compound has three dienophile groups.
A third embodiment of the current invention is a cured polyarylene material comprising the reaction product of 3,3xe2x80x2-(oxydi-1,4-phenylene)bis(2,4,5-triphenylcyclopentadienone) and 1,3,5-tris(phenylethynyl)benzene wherein the stoichiometric molar ratio of the two monomers is between 0.7/1 and 0.99/1, respectively, wherein said polyarylene polymer has been cured at a temperature of at least 405xc2x0 C. for at least one hour, wherein said polyarylene material possesses a coefficient of thermal expansion as determined by thermal mechanical analysis of less than 110 ppm/xc2x0 C. over a temperature range of 350xc2x0-425xc2x0 C.
In the third embodiment, the polyarylene material is a material wherein the most preferable monomer ratio is 0.9/1.
More specifically, the polyarylene material described in the third embodiment is a material wherein the preferred cure profile is 410xc2x0 C. for 90 minutes or 415xc2x0 C. for 60 minutes.
A fourth embodiment of the present invention relates to an integrated circuit article comprising an active substrate containing transistors, an electrical interconnect structure comprising a pattern of metal lines, and one of the polyarylene material described in the third embodiment at least partially separating the lines.